In recent years, simple test reagents or kits for performing a variety of tests such as for the presence of pathogen infection such as a virus or bacteria, or pregnancy are being developed. Detection or quantification of a pathogen component or hormone is the subject of these tests. Many of these simple test reagents are cheap, simple to operate and do not require specific equipment or devices.
For example, pregnancy test reagents are sold at general chemists and pathogen test reagents are widely used in hospitals and surgeries. The importance of simple assay reagents at medical facilities is increasing since medical measures can be taken at an early stage if the presence of an infection is confirmed in a pathogen test.
Presently, an immunoassay method which uses an antigen-antibody reaction is commonly known as a simple test method and a lateral flow test reagent is sold widely. The principle of this test reagent is a method in which a detection sample including a subject to be detected is developed on a nitrocellulose membrane in a horizontal direction, and a composite of a label which binds specifically with the subject to be detected is formed on the membrane. It is possible to detect or quantify the subject to be detected by detecting or quantifying this label.
One form of the lateral flow immunoassay method includes supplying a certain amount of a specimen sample which includes the subject to be detected to a test device arranged with a detection part in which an antibody which specifically binds to a subject to be detected is solid phased as a trapping agent on a membrane strip of nitrocellulose etc, and a labeling component part which includes a label for specifically binding to a subject to be detected, the specimen sample is developed while forming a composite of the subject to be detected and the label, and the label is detected or quantified by trapping the composite with the detection part.
In an assay system which uses the above described membrane, a method in which a gold particle is labeled on an antibody which specifically binds with a subject to be detected as a label is conventionally used. However, recently, an assay system has been established which uses a colored latex particle, a phosphor latex particle and a magnetic latex particle instead of a gold particle and the assay subject continues to expand. In particular, an effective and simple test reagent is greatly expected in the lateral flow immunoassay method, because a wide ranging subject pathogen microbial antigen can be assayed if an antibody can be prepared.
Generally, the time required for an assay (reaction) in the lateral flow immunoassay method is 5 to 15 minutes. A quicker and more sensitive assay method is being demanded as a simple test which requires speed in the detection and treatment of viruses such as the influenza virus, adenovirus and norovirus and thus many improvements are being researched.
The label is used in labeling a latex particle on an antibody which specifically binds to a subject to be detected as a marker and in a state in which the later particle is freeze dried or warm air dried (including natural drying). However, time is required to release and reconstruct the label when detection testing and because the label is sometimes left without being developed, there is a problem in rapid, highly sensitive detection.
As a means for solving this problem, Japanese Laid Open Patent 2008-203135 for example discloses rapidly reconstructing and developing a label within a specimen sample using a surface activating agent and suppressing autoagglutination of a latex particle during a drying process by including a sugar chain.
However, when focusing on a substrate which is included with a label, a material in which glass fiber which is often used as a substrate included with a label such as a latex particle is processed into a sheet has good label release yet tension strength is weak and manufacturing process restrictions are received. In addition, while there are materials such as synthetic fibers which have strong tension strength, release of a label from a label drying pad on which the label is dried on the substrate is poor and are not suited to quick, highly sensitive and simple detection reagents. As a result, until recently, a substrate with good label release and strong tension strength was not used as a label drying pad.